Collimators determine the resolution and sensitivity of the gamma cameras used in planar scintigraphy and single photon emission computed tomography (SPECT) in nuclear medicine. We propose to develop deep x-ray lithography/electroplating method to fabricate collimators. This new method has the following features: (a) Septal walls can be thinner than 100 pm. (b) The technology is applicable to parallel hole as well as converging collimators with continuous focus. (c) Pixels can vary in shape and size in the same plane. (d) The collimator can have non-uniform thickness. High-resolution collimators with optimized sensitivity would be achievable. In Phase 1, we propose to: (a) fabricate parallel hole, lead collimators with septal walls thinner than 100 pm for two small animal gamma-cameras; (b) characterize the collimator t experimentally, and compare the results with theoretical predictions; (c) develop electroplate and polishing technology for gold; (d) develop optimized collimator designs for converging collimators that are no longer restricted by existing collimator fabrication parameter limitations, (e) design various converging beam collimators for a small animal SPECT and (f) perform ray-tracing simulations of these designs. Progress in genome research has stimulated great interest in the development of molecular medicine; this field makes extensive use of knockout-gene, animal models in mice and rats. Non-invasive imaging techniques using radiotracers will play a major role in this effort and collimators is the most crucial element in determining the sensitivity and resolution of images in nuclear medicine.